LIME SHOULD BE KEPT NEAR THE SURrACE. 393 



lo the other. The lime arrests the noxious effluvia which tend to rise 

 more or less from every soil at certain seasons of the year, and decom- 

 poses them or causes their elements to assume new forms of chemical 

 combination, in which they no longer exert the same injurious influ- 

 ence upon animal life. How beautiful a consequence of skilful agri- 

 cuhure, that the health of the community should be promoted by the 

 same methods which most largely increase the produce of the land ! 

 Can you doubt that the All-benevolent places this consequence so 

 plainly before you, as a stimulus to further and more general improve- 

 ment — to the application of other know^ledge still to the amelioration of 

 the soil ? 



§ 16. Circumstances by which the effects of lime are modified. 



These effects of lime are modified by various circumstances. We 

 have already seen that the quantity which must be applied to produce 

 a given effect, and the form in wliich it will prove most advantageous, 

 are, in a great measure, dependent upon the dryness of the soil, upon 

 the quantity of vegetable matter it contains, and on its stiff" or open 1;ex- 

 lure. There are several other circumstances, however, to which it is 

 pro|)er still to advert. Thus, 



1°. Its effects are greatest when well mixed with the soil, and kept 

 near the surface ivithin easy reach of the atmosphere. The reason of 

 this will hereafter appear. 



2°. On arable soils of the same kind and quality, the effects are 

 greatest upon such as are newly ploughed out, or upon subsoils just 

 brought to day. In the case of subsoils, this is owing partly lo their 

 contaitiing naturally very little lime, and partly to the presence of nox- 

 ious ingredients, which lime has the power of neutralizing. In the case 

 of surface soils newly ploughed out, the greater effect, in addition to these 

 two causes, is due also to the large amount of vegetable and other or- 

 ganic matter which has gradually accumulated within them. It is tne 

 presence of this organic matter which has led to the establishment of 

 the excellent practical rule — " that lime ought always to precede putres- 

 cent manures when old leys are broken up for cultivation.^^ 



3^. Its effects are greater on certain geological formations than on 

 others. Thus it produces much effect on drifted (diluvial) sands and 

 clays — on the soils of the plastic and wealden clays (Lee. XL, § 8) — 

 on those of the new and old red sand-stones, of the granites, and of 

 many slate-rocks — and, generally, on the soils formed from all rocks 

 which contain little lime, or from which the lime may have been washed 

 out during their gradual degradation. 



On the other hand, it is often applied in vain to the soils of the oolites 

 (Lee. XL, § 8), and other calcareous formations, because of the abund- 

 ance of lime already present in them. The advantage derived from 

 chalking thin clay soils resting immediately upon the chalk rock (Lee. 

 XL, § 8, and page 376), is explained by the almost entire absence oi 

 lime from these soils. The clay covering of the chalk wolds has pro 

 bably been formed, not from the ruins of the chalk rock itself, but 

 from the tkposit of muddy waters, which rested upon it for some time 

 before those localities became dry land. 



4°. Lime produces a greater proportionzl improvement upon poor soils 



